There are a lot of interesting plants in the spurge genus (Euphorbia), which includes the milkweeds and pointsettias, as well as the plant pictured here: snow-on-the-prairie (Euphorbia bicolor). The name comes from its habit of covering acres of open land with its bright white foliage, looking like snow. There is a closely related species called snow-on-the-mountain, but that plant has wider, shorter leaves.
The attraction of this flower is not in its blossoms, which are tiny, but in its brightly striped foliage. It is a large plant and not suited to cluttered, medium-sized gardens like we have. I have sometimes grown snow-on-the-prairie from seed but it never gets very large or looks healthy. It seems to need wide open spaces, dry conditions, and cow manure. These photos were taken on a ranch outside of Waco, in an area where cattle are kept. The plant wasn't numerous there, but they seemed to be doing well. I've also seen it growing here in Austin in vacant lots and fields, but never as large or full-looking as the well-fertilized ones in a cow pasture.